## Cryptology ePrint Archive: Report 2006/481

A Practical Limit of Security Proof in the Ideal Cipher Model : Possibility of Using the Constant As a Trapdoor In Several Double Block Length Hash Functions

Donghoon Chang

Abstract: Recently, Shoichi Hirose \cite{Hirose06} proposed several double block length (DBL) hash functions. Each DBL hash function uses a constant which has a role to make the DBL hash function collision-resistant in the ideal cipher model. However, we have to instantiate a block cipher. In this paper, we show that the constant may be used as a trapdoor to help a attacker to find a collision easily. In case of 256-bit output size, we can find a collision with the complexity $2^{64}$. This is a gap between the security of the DBL hash function in the ideal cipher model and the security of the DBL hash function based on any block cipher.

Category / Keywords: secret-key cryptography / Hash Function, Collision Attack, Block Cipher, Double Block Length Hash Function, Constant, Trapdoor.

Date: received 21 Dec 2006

Contact author: pointchang at gmail com

Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation

Short URL: ia.cr/2006/481

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